A numerical simulation has been performed of the propagation of an action potential through a thick cylindrical strand of cardiac tissue. The bidomain model was used to account for the effect of tissue anisotropy and the interstitial space on current flow, and the Beeler-Reuter model was used for the electrically active membrane properties. A relaxation technique was used to solve the nonlinear partial differential equations. The simulation predicts: 1) the shape of the wavefront across the strand cross-section, 2) the dependence of the conduction velocity on the strand radius and on the radii of the individual cells, 3) the length constant of the tissue, as measured by subthreshold cable analysis, and how it is affected by tissue anisotropy, and 4) the effect of tissue edema (changes in the volume fraction of the extracellular space) on propagation.